JP2003172363A - Rolling bearing, and manufacture of outer ring for rolling bearing - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a rolling bearing capable of preventing early breakage or plastic deformation of an outer ring. <P>SOLUTION: This rolling bearing comprises an inner ring, an outer ring 1 used as a roll with its outer periphery contacting with other members, and a plurality of rolling elements arranged between both of the inner and outer rings. The hardness of a portion 3 from an outer periphery 2 of the outer ring 1 to depth of 3 mm is set to 58-62 in Rockwell C hardness (HRC). The hardness gradient of the depth portion 3 is set to 1 HRC/1 mm or less from the outer periphery toward the inside. The amount of residual austenite at the depth portion 3 is set to 5-18 vol%. The hardness of a portion 5 from an inner periphery 4 of the outer ring 1 to depth of 1 mm is set to 61-64 HRC. The amount of residual austenite at the depth portion 5 is set to 5-15 vol%. The hardness of a center part in a thickness direction between the inner and outer peripheries 4 and 2 of the outer ring 1 is set to 35-42 HRC. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rolling bearing and a rolling bearing provided with an inner ring, an outer ring whose outer peripheral surface contacts another member and is used as a roll, and a plurality of rolling elements arranged between the inner and outer rings. The present invention relates to a method for manufacturing a bearing outer ring.

[0002]

2. Description of the Related Art For example, an outer ring of a rolling bearing is used for a backup roll of a multi-stage rolling mill. Such rolling bearings are often used with lubricating oil containing foreign matter, and it is of course necessary to extend rolling fatigue life under lubricating conditions with lubricating oil containing foreign matter. However, fracture resistance of the outer ring and deformation resistance against plastic deformation due to heat and load of the outer ring are required. If the outer ring is broken, it will cause a line stop on the rolling line,
This is because rolling quality deteriorates when the outer ring is plastically deformed.
Normally, regular inspections are carried out to prevent such line stop of rolling lines and deterioration of rolling quality.
Rolling bearings are replaced before they are damaged.

However, if the outer ring of the rolling bearing used as a backup roll is broken or plastically deformed in a short period of time, the above-mentioned regular inspection needs to be performed in a relatively short period, which is troublesome.

Conventionally, in order to prevent cracking and plastic deformation of the outer ring, the outer ring material formed in a predetermined shape using bearing steel is carburized or carbonitrided to harden the outer surface of the outer ring. The surface hardened layer having a relatively large thickness is formed, and toughness is imparted to the inside of the hardened layer.

[0005]

By the way, a rolling bearing having an outer ring used as a backup roll of a multi-stage rolling mill is a bearing of high load capacity, and when the outer peripheral surface of the outer ring is scratched. Since it is necessary to re-polish to remove this scratch, it is necessary to increase the thickness of the surface-hardened layer.

However, in order to form a thick surface-hardened layer by carburizing or carbonitriding, it is necessary to prolong the processing time, which causes a problem of high manufacturing cost.

An object of the present invention is to solve the above problems and to provide a rolling bearing capable of preventing the outer ring from being damaged or plastically deformed in a short period of time, and a method of manufacturing an outer ring for a rolling bearing capable of reducing the manufacturing cost. To provide.

[0008]

A rolling bearing according to the invention of claim 1 is arranged between an inner ring, an outer ring which is used as a roll with its outer peripheral surface contacting other members, and both inner and outer rings. In a rolling bearing having a plurality of rolling elements, the hardness of the portion from the outer peripheral surface of the outer ring to a depth of 3 mm is 58 to 62 in Rockwell C hardness (HRC) and the hardness of this depth portion The slope is 1 HR from the outer circumference to the inside
C / 1mm or less, the amount of retained austenite in this depth portion is 5-18vol%, and the hardness of the portion from the inner peripheral surface of the outer ring to the depth 1mm is 61-64HRC and this depth The amount of retained austenite in the portion is 5 to 15 vol%, and the hardness of the central portion in the thickness direction between the inner and outer peripheral surfaces of the outer ring is 35 to 42 HRC.

The reason for limiting each numerical value in the invention of claim 1 is as follows.

From the outer peripheral surface of the outer ring to the depth of 3 mm
Hardness If the hardness is less than 58 HRC, plastic deformation is likely to occur, and if it exceeds 62 HRC, cracking is likely to occur.

From the outer peripheral surface of the outer ring to the depth of 3 mm
Hardness gradient If this gradient exceeds 1 HRC / 1 mm, surface cracks develop. That is, in order to prevent the development of surface cracks and improve the fracture resistance, it is effective to increase the compressive residual stress, but it is effective to increase the compressive residual stress from the outer peripheral surface of the outer ring to a depth of 3 mm. In order to increase the hardness, it is necessary that the hardness gradient is 1 HRC / 1 mm or less and uniform.

From the outer peripheral surface of the outer ring to the depth of 3 mm
Amount of retained austenite If the amount of retained austenite is less than 5 vol%, toughness is insufficient and fracture resistance decreases, and if it exceeds 18 vol%, aging deformation easily occurs and dimensional deformation occurs, resulting in locally high surface pressure. This is because the occurrence of the point causes breakage.

Here, the hardness, the hardness gradient and the amount of retained austenite in the portion from the outer peripheral surface of the outer ring to the depth of 3 mm are set as described above in order to enable reuse of the outer ring once used. is there. That is, it is possible to reuse the outer peripheral surface of the outer ring once used by polishing (re-polishing). However, in order to obtain desired performance after polishing, the outer peripheral surface of the outer ring must have a depth of 3 mm or less. The hardness of the part, the hardness gradient and the amount of retained austenite must be set as described above.

From the inner peripheral surface of the outer ring to the depth of 1 mm
Hardness If the hardness is less than 61 HRC, indentation due to foreign matter is likely to occur, and if it exceeds 64, cracking is likely to occur.

From the inner peripheral surface of the outer ring to a depth of 1 mm
Amount of retained austenite If the amount of retained austenite is less than 5 vol%, toughness is insufficient and fracture resistance is reduced, and the life for foreign matter is reduced, and if it exceeds 15 vol%, aging deformation is likely to occur and dimensional deformation occurs. The reason is that locally high surface pressure points are generated to cause fracture and the rolling life is shortened.

Here, the hardness and the amount of retained austenite in the portion from the inner peripheral surface of the outer ring to the depth of 1 mm are set as described above, because the maximum shear stress depth which governs the internal origin peeling life is within 1 mm. Because it has become.

The center portion in the thickness direction between the inner and outer peripheral surfaces of the outer ring is
Hardness If this hardness is less than 35 HRC, plastic deformation is likely to occur, resulting in insufficient strength. For example, if it exceeds 42 HRC, toughness becomes insufficient and fracture resistance decreases. Because it does.

According to the rolling bearing of the first aspect of the present invention, for example, when used as a backup roll of a multi-high rolling mill, cracking due to surface crack development of the outer ring in a short period of time or plastic deformation of the outer ring in a short period of time. Can be prevented. Therefore, the life of the outer ring can be extended.

A rolling bearing according to a second aspect of the present invention is the rolling bearing according to the first aspect of the present invention, wherein the surface hardness of the outer ring at both end surfaces thereof except the annular portion having a width of 3 mm and the inner peripheral edge excluding the annular portion having a width of 1 mm. Is 45 to 59 HRC.

According to the second aspect of the present invention, the surface hardness of the outer ring at both end surfaces of the outer ring excluding the annular portion having a width of 3 mm and the inner peripheral edge excluding the annular portion having a width of 1 mm is 45 to 45.
The reason why it is limited to 59 HRC is that if it is less than 45 HRC, the strength of the entire bearing outer ring becomes insufficient, and if it exceeds 59 HRC, the fracture resistance of the bearing outer ring becomes insufficient.

According to the second aspect of the present invention, even if heat cracks occur in both end faces of the outer ring and the thrust washers adjacent thereto, the entire outer ring of the bearing is prevented from being broken.

A method for manufacturing an outer ring for a rolling bearing according to a third aspect of the present invention is a method for manufacturing an outer ring for a rolling bearing according to the first aspect, which is a method for producing an outer ring for a rolling bearing according to the first aspect. C 0.8-1.3 wt%, Si 0.35-
0.8 wt%, Mn 0.3 to 1.2 wt%, Cr 0.9 to
The outer ring material formed into a predetermined shape by using steel containing 1.5 wt% and the balance Fe and unavoidable impurities is
After heating at 0 to 880 ° C for 1 to 3 hours, quenching is performed in quenching oil, and the pressure of 0.2 to 0.2 is applied to the inner peripheral surface of the outer ring material during quenching oil.
The same outer circumference as well as injecting the quenching oil in 0.8 kg / cm ² and is characterized in that injecting the quenching oil pressure 1.4~2.1kg / cm ^2.

The reason for limiting each numerical value in the invention of claim 3 is as follows.

Steel type C Content C is an essential element for maintaining the strength as a bearing, and if the content is less than 0.8 wt%, the hardness of the inner and outer peripheral surfaces of the outer ring after quenching and tempering It becomes difficult to obtain the desired hardness for each of them, and the rolling life decreases, and if it exceeds 1.3 wt%, huge carbides are likely to be generated in the melting stage of the steel material, which deteriorates workability and resistance to fracture. This is because the durability and rolling fatigue life are reduced.

Si content Si has the property of improving the rolling life, but if the content is less than 0.35 wt%, it is difficult to obtain the rolling life improving effect, and if it exceeds 0.8 wt%, the hardness after softening heat treatment is reduced. This is because it becomes higher and machinability and forgeability are significantly deteriorated.

Mn content Mn is used as a deoxidizing agent and at the same time has the property of improving hardenability and rupture resistance, but if the content is less than 0.3 wt%, the smelting cost is high. It becomes 1.
This is because if it exceeds 2 wt%, the machinability will drop sharply.

Cr content Cr has the property of improving hardenability, rupture resistance and rolling life, but if the content is less than 0.9 wt%, the effect of improving rupture resistance and rolling life can be obtained. No, 1.5
This is because when it exceeds wt%, large carbides are formed and the fracture resistance and rolling life are rather deteriorated.

Heating Temperature If the heating temperature is less than 800 ° C., the hardness of both the inner and outer peripheral surfaces of the outer ring cannot be made to be the desired hardness, and if it exceeds 880 ° C., coarsening of crystal grains proceeds and the second phase This is because the solid solution of the above-mentioned carbide in the matrix becomes too large, and the required rolling life and fracture resistance cannot be obtained.

Heating time If the heating time is less than 1 hour, heat treatment will be defective due to insufficient soaking, and if it exceeds 3 hours, the heat treatment cost will increase.

Quenching oil on the inner and outer peripheral surfaces of the outer ring material
When the injection pressure of the quenching oil to the inner peripheral surface and the outer peripheral surface of the outer ring material is less than the lower limit value, the hardness of the inner peripheral surface and the outer peripheral surface of the outer ring cannot be set to a predetermined hardness. This is because if the upper limit is exceeded, the internal hardness becomes too hard and becomes greater than 42 HRC. The injection pressure is the pressure at the injection port of the injection nozzle. Further, the injection port of the nozzle for injecting the quenching oil onto the outer peripheral surface of the outer ring material is 15
It is preferable that they are separated by 0 to 300 mm, and 200 to 2
It is desirable that they are separated by 50 mm.

According to the invention of claim 3, the hardness of the portion from the outer peripheral surface to the depth of 3 mm is Rockwell C hardness (HRC).
And the hardness gradient at this depth becomes 1HRC / 1mm or less from the outer peripheral surface toward the inside,
Furthermore, the amount of retained austenite in this depth portion is 5 to 18
It is possible to manufacture an outer ring in which the hardness of the portion from the inner peripheral surface to the depth of 1 mm is 61 to 64 HRC and the retained austenite amount in this depth portion is 5 to 15 vol%.

Then, the outer ring material is heated at 800 to 880 ° C. for 1 to 3 hours and then quenched in quenching oil, and the pressure of 0.2 to 0. 8 kg / cm ²
Quenching oil is injected at the same time and pressure on the outer peripheral surface is 1.4
Since it only sprays quenching oil at ~ 2.1 kg / cm ² ,
The cost is lower than the conventional method of carburizing or carbonitriding.

A method for manufacturing an outer ring for a rolling bearing according to a fourth aspect of the present invention is the method for manufacturing an outer ring for a rolling bearing according to the second aspect of the present invention, wherein the outer ring for rolling bearing is quenched during quenching. , Width 3mm from the outer edge of both ends of the outer ring material
The annular portion and the inner peripheral edge portion excluding the annular portion having a width of 1 mm are covered with a ring made of steel.

In this case, by appropriately adjusting the thickness of the ring, it becomes possible to adjust the hardness after quenching of the portions of the outer ring material covered by the ring on both end surfaces,
As a result, the hardness of the part covered by the ring is 45 to 59 HRC, which is softer than the hardness of both the inner and outer peripheral surfaces of the outer ring after quenching.
Can be For example, if the ring thickness is 5 mm
In such a case, the hardness of the portion covered with the ring on both end surfaces of the outer ring after quenching is the hardness of the portion having a depth of 5 mm from the surface when not covered with the ring.

[0035]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings.

In FIG. 1, which shows an outer ring of a rolling bearing used as a backup roll of a multi-stage rolling mill, the outer ring is shown in FIG.
The hardness of the portion (3) from the outer peripheral surface (2) of (1) to the depth of 3 mm is 58 to 62 in Rockwell C hardness (HRC), and the hardness of this depth portion (3) The gradient is 1 HRC / 1 mm or less from the outer peripheral surface (2) toward the inside. Also,
The hardness of the portion (5) from the inner peripheral surface (4) of the outer ring (1) to the depth of 1 mm is 61 to 64 HRC, and it is between the inner and outer peripheral surfaces (4) and (2) of the outer ring (1). The hardness of the central part in the thickness direction is 35 to 42 HRC
Has been made. The hardness distribution of the outer ring (1) in the thickness direction changes smoothly from both the inner and outer peripheral surfaces (4) and (2) to the central portion in the thickness direction. Further, the amount of retained austenite in the portion (3) from the outer peripheral surface (2) of the outer ring (1) to the depth of 3 mm is 5 to 5.
18 vol%, 1m deep from the inner surface (4) of the outer ring (1)
The amount of retained austenite in the part (5) up to m is 5 to 15 vol.
It is said to be%.

The surface hardness of the outer ring (1) excluding the annular portion (7) with a width of 3 mm and the annular portion (8) with a width of 1 mm from the outer peripheral edge of both end surfaces (6) is 45 to 59 HRC. Has been made.

The outer ring (1) as described above is manufactured by the method described below.

First, C 0.8 to 1.3 wt% and Si 0.3
5 to 0.8 wt%, Mn 0.3 to 1.2 wt%, Cr 0.9
An outer ring material (10) having a predetermined shape is formed by using steel containing ˜1.5 wt% and the balance Fe and unavoidable impurities.
Then, the outer ring material (10) is heated at 800 to 880 ° C. for 1 to 3 hours and then quenched in quenching oil. Before this quenching,
As shown in FIG. 2, the outer ring material (10) is covered with a ring (11) made of a steel material at both ends of the outer peripheral edge except for an annular portion having a width of 3 mm and an inner peripheral edge excluding an annular portion having a width of 1 mm. , Fix both rings (11) with clips not shown. Further, as shown in FIG. 3, during quenching, the first quenching oil injection nozzle (12) extending in the axial direction on the central axis on the inner peripheral side of the outer ring material (10) during quenching oil is installed. In addition to arranging one, second quenching oil injection nozzles (13) extending in the axial direction are respectively arranged at a plurality of locations on the outer peripheral side of the outer ring material (10) at equal intervals in the circumferential direction, and the outer ring material is arranged. The first quenching oil injection nozzle (12) injects quenching oil at a pressure of 0.2 to 0.8 kg / cm ² onto the inner peripheral surface of (10), and the second quenching oil injection nozzle ( 13) pressure 1.
Inject quenching oil at 4-2.1 kg / cm ² .

After the quenching is finished, the outer ring material (10) is taken out from the quenching oil, the ring (11) is removed, and a tempering process is performed.
Finally, the inner and outer peripheral surfaces and both end surfaces of the outer ring material (10) are subjected to a predetermined cutting process or the like. Thus, the outer ring (1) is manufactured.

Next, specific examples of the present invention will be described.

C1.02 wt%, Si0.55 wt%, Mn
1.01 wt%, P0.015 wt%, S0.003 wt%,
Cu 0.09 wt%, Ni 0.07 wt%, Cr 1.10 wt
% And Mo 0.02 wt%, with the balance Fe and unavoidable impurities, the outer diameter is 300 mm and the inner diameter is 2
A cylindrical outer ring material (10) having a length of 20 mm and a length of 170 mm was formed.

Then, the outer ring material (10) was heated to 100 at 860 ° C.
After heating for 5 minutes, the outer ring material (10) has both ends with an annular portion with a width of 3 mm and an inner peripheral edge excluding an annular portion with a width of 1 mm on both end faces, and has a thickness of 5 m made of JIS S45C.
m ring (11) and both rings (11) were fixed with clips. Then, the outer ring material (10) is immersed in quenching oil consisting of master quench A at an oil temperature of 80 ° C. to quench it, and the first quenching oil injection nozzle (12) in the quenching oil.
To inject quenching oil to the inner peripheral surface of the outer ring material (10) at a pressure of 0.6 kg / cm ² and also to the second quenching oil injection nozzle (1
By 3), quenching oil was sprayed on the outer peripheral surface at a pressure of 1.9 kg / cm ² . The number of the second quenching oil injection nozzles (13) is eight. Quenching conditions are shown in Table 1.

[0044]

[Table 1]

After the quenching was completed, the outer ring material (10) was taken out from the quenching oil, the ring (11) was removed, and a tempering treatment was carried out by heating at 200 ° C. for 5 hours. Then, the inner and outer peripheral surfaces and both end surfaces of the outer ring material (10) were subjected to predetermined cutting and grinding.

Thus, the hardness distribution from the outer peripheral surface (2) to the inner peripheral surface (3) at the center of the length of the manufactured outer ring (1) was measured. As a result, as shown in FIG. 4, the outer peripheral surface (2)
Has a hardness of 61 HRC and a portion (3) 3 mm deep from the outer peripheral surface (2)
Has a hardness of 59 HRC, and the part from the outer peripheral surface (2) to a depth of 3 mm
The hardness gradient of (3) is 2/3 HR from the outer peripheral surface (2) toward the inside
It was C / 1 mm. The hardness of the inner surface (4) is 62HR.
C, the hardness of the part (5) with a depth of 1 mm from the inner peripheral surface (4) is 61 HR
C, the hardness at the center in the thickness direction was 39 HRC. Furthermore, the retained austenite amount in the portion (3) from the outer peripheral surface (2) to the depth of 3 mm is 11 vol%, and the retained austenite amount in the portion (5) from the inner peripheral surface (4) to the depth of 1 mm is 13 vol%. Was there.

Further, when the rolling bearing is assembled by using the outer ring (1) manufactured as described above, and the outer ring (1) is incorporated into the multi-stage rolling mill so as to serve as a backup roll, the conventional outer ring is used. No damage or plastic deformation was observed on the outer ring (1) even after 6 months of use, which required inspection and replacement when using.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view showing a half of an outer ring of a rolling bearing according to the present invention.

FIG. 2 is a vertical cross-sectional view showing a state in which a ring is attached to a heated outer ring material.

FIG. 3 is a view showing an arrangement state of nozzles for injecting the quenching oil onto the outer race material during quenching oil.

FIG. 4 is a graph showing a hardness distribution of an outer ring manufactured in a specific example.

[Explanation of symbols]

(1): Outer ring (2): Outer peripheral surface (3): Part from the outer peripheral surface to a depth of 3 mm (4): Inner surface (5): From the inner peripheral surface to a depth of 1 mm (6): End face (7): An annular portion with a width of 3 mm from the outer peripheral edge (8): An annular portion with a width of 1 mm from the inner peripheral edge

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) // C22C 38/00 301 C22C 38/00 301Z 38/18 38/18 38/44 38/44 F term ( Reference) 3J101 AA01 BA54 BA70 DA03 EA03 FA15 FA31 FA44 GA36 3J103 AA02 AA12 AA41 CA26 EA11 EA12 FA03 FA12 FA14 GA02 GA15 HA03 HA14 HA15 HA32 4K042 AA22 BA03 CA05 CA06 CA08 CA10 DA01 DA02 DD03 DD04

Claims (4)

[Claims] 1. A rolling bearing comprising an inner ring, an outer ring whose outer peripheral surface comes into contact with another member to be used as a roll, and a plurality of rolling elements arranged between the inner and outer rings. The hardness of the portion up to 3 mm is 58 to 62 in Rockwell C hardness (HRC), and the hardness gradient of this depth portion is 1 HRC / 1 mm or less from the outer peripheral surface to the inner side. The amount of retained austenite in the depth is 5 to 18 vol%, and the depth is 1 from the inner surface of the outer ring.
The hardness of the part up to mm is made 61 to 64 HRC and the amount of retained austenite at this depth is 5 to 15 vo
The rolling bearing is characterized in that the hardness of the central portion in the thickness direction between the inner and outer peripheral surfaces of the outer ring is 35 to 42 HRC. 2. A width of 3 m from the outer peripheral edges of both end faces of the outer ring.
2. The rolling bearing according to claim 1, wherein a surface hardness of an annular portion of m and an inner peripheral edge thereof excluding the annular portion having a width of 1 mm is 45 to 59 HRC. 3. A method for manufacturing an outer ring of a rolling bearing according to claim 1, wherein C0.8-1.3 wt% and Si0.35-
0.8 wt%, Mn 0.3 to 1.2 wt%, Cr 0.9 to
The outer ring material formed into a predetermined shape by using steel containing 1.5 wt% and the balance Fe and unavoidable impurities is
After heating at 0 to 880 ° C for 1 to 3 hours, quenching is performed in quenching oil, and the pressure of 0.2 to 0.2 is applied to the inner peripheral surface of the outer ring material during quenching oil.
Method of manufacturing a rolling bearing outer ring, characterized in that also injects quenching oil pressure 1.4~2.1kg / cm ² on the outer circumferential surface with injecting a quenching oil in 0.8 kg / cm ^2. 4. A method for manufacturing an outer ring of a rolling bearing according to claim 2, wherein at the time of quenching into quenching oil, an annular portion having a width of 3 mm from the outer peripheral edge and a width from the inner peripheral edge on both end faces of the outer ring material. The method for manufacturing an outer ring for a rolling bearing according to claim 3, wherein a portion made of a steel material is covered except for the 1 mm annular portion.